Excessive cytokine production is an important component of the acute respiratory distress syndrome and multiple organ failure. Pneumonia can lead to an overexpression of cytokines, although comparatively little is known about the relevance and differences in cytokines between blood and lung. In this study, piglets were experimentally infected intranasally with Actinobacillus pleuropneumoniae (APP), and transcriptomes of lung tissue and peripheral blood mononuclear cells determined. In addition, the levels of 30 cytokines in broncheoalveolar lavage fluid (BALF) and sera were determined by ELISA. Post infection, there was an early increase in lung monocytes, and a later rise in inflammatory cytokines in BALF. Blood lymphocytes increased early in infection and there was a rise in inflammatory cytokines in the peripheral blood of infected piglets. Genes involved in cytokine production, leukocyte migration and differentiation, lymphocyte activation, and cytokine-mediated signaling pathways in the transcriptomes of lung tissue were significantly down-regulated early in infection. At this early phase of APP infection (0−6 h), the cytokines IL-1β, MCP-1, and IL-5 in sera increased rapidly and significantly, while many cytokines in BALF decreased. At 48 h post-infection, cytokines in sera were no longer significantly increased, although some were up-regulated in BALF, and there was aggravated pathological damage in the lungs at this time.

The data indicate there are substantial differences between immune cells and cytokines in the lung and peripheral blood of APP infected piglets at equivalent time points. The results increase our understanding of pig-APP host interactive biology, and will be important in formulating future therapeutic and preventative strategies to prevent disease caused by APP.

细胞因子产生过多是急性呼吸窘迫综合征和多器官衰竭的重要组成部分。肺炎可导致细胞因子过度表达，尽管人们对血液和肺部细胞因子之间的相关性和差异知之甚少。在这项研究中，实验性地用胸膜肺炎放线杆菌（APP）鼻内感染仔猪，并测定肺组织和外周血单核细胞的转录组。此外，还通过ELISA测定了支气管肺泡灌洗液(BALF)和血清中30种细胞因子的水平。感染后，肺单核细胞早期增加，BALF 中炎症细胞因子随后增加。感染早期血液淋巴细胞增加，感染仔猪外周血中炎症细胞因子增加。肺组织转录组中涉及细胞因子产生、白细胞迁移和分化、淋巴细胞活化以及细胞因子介导的信号通路的基因在感染早期显着下调。在APP感染的早期阶段（0~6小时），血清中的细胞因子IL-1β、MCP-1和IL-5迅速而显着增加，而BALF中的许多细胞因子减少。感染后48小时，血清中细胞因子不再明显升高，但BALF中部分细胞因子上调，此时肺部病理损伤加重。

数据表明，相同时间点APP感染仔猪的肺和外周血中的免疫细胞和细胞因子存在显着差异。这些结果增加了我们对猪-APP宿主相互作用生物学的理解，对于制定未来预防APP引起的疾病的治疗和预防策略具有重要意义。